Rename "container" to "image"

- Updated `wwctl upgrade` to handle updates
- Maintained `.Container` and `.ContainerName` in tstruct
- Added `ContainerName()` methods to node and profile objects
- Added `--container`, `-C` aliases to wwctl commands (`<node|profile> <add|set>`)
- Added `wwctl container` alias
- Added support for `container_exit.sh` if `image_exit.sh` is not found

Signed-off-by: Jonathon Anderson <janderson@ciq.com>

userdocs/contributing/debugging.rst

@@ -239,7 +239,7 @@ Example debugging session
    altvalue: []string len: 0, cap: 0, nil,
    from: "",
    def: []string len: 0, cap: 0, nil,},
-   ContainerName: github.com/warewulf/warewulf/internal/pkg/node.Entry {
+   ImageName: github.com/warewulf/warewulf/internal/pkg/node.Entry {
    value: []string len: 0, cap: 0, nil,
    altvalue: []string len: 0, cap: 0, nil,
    from: "",

userdocs/contributing/development-environment-kvm.rst

@@ -101,8 +101,8 @@ Build and install Warewulf on wwdev
    sudo wwctl configure nfs  # Configure NFS exports
    sudo wwctl configure ssh  # Build the basic ssh keys to be included by the ssh overlays
 
-   # Pull and build the VNFS container and kernel
-   sudo wwctl container import docker://ghcr.io/warewulf/warewulf-centos:7 centos-7 --setdefault
+   # Pull and build the image and kernel
+   sudo wwctl image import docker://ghcr.io/warewulf/warewulf-centos:7 centos-7 --setdefault
    sudo wwctl kernel import build $(uname -r) --setdefault
 
    # Set up the default node profile

userdocs/contributing/development-environment-vagrant.rst

@@ -223,8 +223,8 @@ Vagrantfile
 
                 wwctl configure --all
 
-                wwctl container import docker://ghcr.io/warewulf/warewulf-rockylinux:9 rocky-9
-                wwctl profile set --yes --container rocky-9 "default"
+                wwctl image import docker://ghcr.io/warewulf/warewulf-rockylinux:9 rocky-9
+                wwctl profile set --yes --image rocky-9 "default"
                 wwctl profile set --yes --netdev eth1 --netmask 255.255.255.0 --gateway 192.168.200.254 "default"
 
                 wwctl node add n0001.cluster -I 192.168.200.101 --discoverable true

userdocs/contributing/development-environment-vbox.rst

@@ -116,8 +116,8 @@ I have VirtualBox running on my desktop.
    sudo wwctl configure nfs  --persist # Configure the NFS exports
    sudo wwctl configure ssh  --persist # Build the basic ssh keys to be included by the SSH overlay
 
-   # Pull and build the VNFS container and kernel
-   sudo wwctl container import docker://ghcr.io/warewulf/warewulf-centos:7 centos-7 --setdefault
+   # Pull and build the image and kernel
+   sudo wwctl image import docker://ghcr.io/warewulf/warewulf-centos:7 centos-7 --setdefault
    sudo wwctl kernel import build $(uname -r) --setdefault
 
    # Set up the default node profile